Downhole well pump assembly

ABSTRACT

Downhole well pump assembly (1) having first and second pump units (7a, 7b) with first and second bellows (31) connected to inlet and outlet check valves. A drive fluid assembly (5) with first and second hydraulic drive lines (9a, 9b) communicates with the bellows. Hydraulic fluid is provided to the first and second hydraulic drive lines. A drive fluid distribution valve (11) is arranged between a drive pump (17) and the drive lines. It has a drive fluid inlet and outlet (113, 115), and first and second drive ports. The distribution valve (11) interchanges between a first mode, where the drive fluid inlet communicates with the first drive port and the drive fluid outlet (115) communicates with the second drive port; and a second mode, wherein the drive fluid inlet communicates with the second drive port, and the drive fluid outlet communicates with the first drive port.

The present invention relates to a downhole well pump assembly suitedfor pumping fluids within the well upwards through the well, string ortubing, towards the surface. Such pumps have been known for some time.However, challenges are still encountered as conditions in the well maybe harsh and the costs associated with such pumps and their replacementor repair, are substantial.

BACKGROUND

US patent application publication US2003042017 describes a submersiblewell pumping system which uses two diaphragm pumps. In this solutioneach of the two pump units have a pump chamber with walls constituted bya diaphragm, so that the volume within the pump chamber can be changedby supplying a hydraulic drive fluid with a reciprocating action. Thereciprocating flow of drive fluid is controlled by a two statesnap-acting valve, which in turn is controlled by a control valve whichsenses the differential pressure across the working diaphragm andgenerates a hydraulic signal to change the state of the two state snapacting valve.

Patent publication U.S. Pat. No. 3,749,526 discloses a pumping apparatusthat comprises two tanks. Each tank is divided into two chambers by abellows. Fluid is pumped by reciprocating the bellows in each tank.

U.S. Pat. No. 3,524,714 discloses a similar pump, which operates byreciprocating a bellows in a respective tank.

As the drive fluid is made to flow back and forth into a first and asecond pump chamber, it is advantageous to avoid mechanical movements orrotations which change direction. Such change of direction may result ina loss of lubricating oil film on mechanical parts, and hence toincreased wear of such parts. Consequently, an object of the inventionis to provide a downhole well pump, wherein its mechanical moving partsis not reciprocating, but are rather moved in a continuous, non-haltingmovement. This will contribute to maintaining the lubricating oil filmon the mechanical parts, and thus enhance the lifetime of the pump.

Another object of the invention is to enhance the lifetime of the pumpunits themselves, i.e. in addition to the drive fluid assembly whichdrives them. As mentioned above, conditions in a well bore may be harsh.For instance, the pump units may be exposed to acidic fluids, sand andwax and high temperatures, for instance in the area of 300° C.

THE INVENTION

According to a first aspect of the present invention, there is provideda downhole well pump assembly having a first pump unit and a second pumpunit. Each pump unit has a compressible metal bellows arranged in ahousing. The housing is connected to an inlet check valve and an outletcheck valve. The assembly further has a drive fluid assembly with afirst hydraulic drive line in communication with the inner volume of themetal bellows of the first pump unit and a second hydraulic drive linein communication with the inner volume of the metal bellows of thesecond pump unit. The drive fluid assembly further comprises a drivefluid pump providing hydraulic fluid to the first and second hydraulicdrive lines and which is mechanically connected to a drive motor that ispowered through a power line. According to the first aspect of thepresent invention, a drive fluid distribution valve is arranged betweenthe drive fluid pump and the first and second hydraulic drive lines.Moreover, the drive fluid distribution valve has a drive fluid inlet, adrive fluid outlet, a first drive port and a second drive port. Thedrive fluid distribution valve is interchangeable between a first modeand a second mode. In the first mode the drive fluid inlet is incommunication with the first drive port, and the drive fluid outlet isin communication with the second drive port. In the second mode, thedrive fluid inlet is in communication with the second drive port, andthe drive fluid outlet is in communication with the first drive port.

The drive fluid pump and the drive motor can be arranged as one singlecomponent.

The drive motor can be any appropriate type of motor, for instance anelectric motor or a hydraulic motor, powered through an electric powerline or a hydraulic power line, respectively. A gas/steam powered drivercan also be used.

The drive fluid distribution valve is so configured, that it receivesdrive fluid through its drive fluid inlet, and distributes the drivefluid to either the first or the second drive port in an alternatingfashion. Correspondingly, it exports drive fluid out through the drivefluid outlet, while receiving the drive fluid through either the firstor the second drive port, also in an alternating fashion. Thus, thedrive fluid distribution valve can receive the drive fluid through onesingle inlet, and export it through one single outlet, while alternatingwhich drive port is guiding drive fluid to one of the pump units, andwhich drive port is receiving drive fluid from the other pump unit.

The drive fluid distribution valve can be in the form of a hydraulicsliding valve, where the position of the sliding valve body governs themode (first or second mode) of the valve. This type of drive fluiddistribution valve will need some sort of valve control means, such aselectric actuation of the sliding valve body. As will appear in thefollowing, however, advantageous embodiments may include another type ofdrive fluid distribution valve.

The housing of the pump unit(s) is advantageously cylindrical. Moreover,the first and second pump units, as well as the drive fluid assembly,are arranged in a row, thus forming a tubular shape. Such an arrangementof the downhole well pump assembly makes it suitable for beingintegrated or installed as a part of casing, liner, production/welltubing or in open hole. The downhole pump can be installed and operatedusing wire(line), umbilical, different pipes, coiled tubing, othertubing and in the open cavity of the well.

In an embodiment of the downhole well pump assembly according to thefirst aspect of the invention, the drive fluid pump has a rotatingoutput which is functionally connected to the drive fluid distributionvalve. In such an embodiment, rotation of the rotating output willgovern the changing of the drive fluid distribution valve between thefirst mode and the second mode.

Advantageously, a reduction gear can be arranged functionally betweenthe rotating output of the drive fluid pump, and the drive fluiddistribution valve.

A bypass channel may be arranged between the first hydraulic drive lineand the second hydraulic drive line. In some embodiments, the bypasschannel can be integrated with the drive fluid distribution valve. Inother embodiments, it may be arranged outside the drive fluiddistribution valve, between the first and second hydraulic drive lines.

Moreover, the compressible bellows in the first and second pump unitsmay comprise a collapse restriction means, wherein the collapserestriction means has a drive fluid valve member which isinterchangeable between an open and a closed position.

When the drive fluid valve member is in the open position, drive fluidmay flow out of the bellows. However, when the drive fluid valve memberis in the closed position, it shuts off the fluid flow out from thebellows. Thus, when in the closed position, the drive fluid valve memberrestricts the bellows from collapsing further.

In embodiments including the collapse restriction means, the drive fluidvalve member can be arranged at a drive fluid inlet and outlet end ofthe compressible bellows, and a bellows closure flange can be arrangedat the opposite end of the compressible bellows. An actuation member,connected to the bellows closure flange, can then protrude axially intocompressible bellows and be configured to abut and thereby move thedrive fluid valve member into the closed position upon movement of thebellows closure flange towards the drive fluid inlet and outlet end.

In some embodiments of the downhole well pump assembly according to theinvention, the drive fluid distribution valve comprises a housing, afirst distribution chamber communicating with the drive fluid outlet, asecond distribution chamber communicating with the drive fluid inlet, afirst drive channel arranged between the first drive port and the firstand second distribution chambers, and a second drive channel arrangedbetween the second drive port and the first and second distributionchambers. The drive fluid distribution valve can further comprise arotatable first distribution member which is arranged between the firstdistribution chamber and the first and second drive channels and whichhas a distribution aperture, and a rotatable second distribution memberwhich is arranged between the second distribution chamber and the firstand second drive channels, and which has a distribution aperture. Eachdistribution aperture of the first distribution member and the seconddistribution member is then adapted to align with both and oppositefirst and second drive channels, depending on the rotational position ofthe first and second distribution members.

Thus, in such embodiments, each of the first and second distributionmembers can be rotated so that they provide fluid communication betweenone of the distribution chambers and one of the first or second drivechannels. The first and second distribution members are mutuallyarranged in such way that while one distribution member provides fluidcommunication between the first distribution chamber and one of thedrive channels, the other distribution member provides fluidcommunication between the second distribution chamber and the otherdrive channel. Hence, the position of the first and second distributionmembers, and their respective distribution apertures, governs the modeof the assembly, i.e. the first and second mode. The first and seconddrive channels alternate between being a drive fluid delivery channeland a drive fluid return channel.

In some embodiments, the first and second distribution members can beconnected to a common shaft. The shaft can be connected to a reductiongear. Moreover, the reduction gear can be connected to the rotatingoutput.

In a preferred embodiment, the bypass channel is a part of the fluiddistribution valve. However, in other embodiments, the bypass channelcan be a separate component that connects the first and second hydraulicdrive lines in an external position with respect to the drive fluiddistribution valve.

According to a second aspect of the present invention, there is provideda fluid distribution valve comprising a housing, a drive fluid inlet, adrive fluid outlet, a first drive port and a second drive port.According to the second aspect of the invention, the fluid distributionvalve comprises a first distribution chamber in fluid communication withthe drive fluid outlet, a second distribution chamber in fluidcommunication with the drive fluid inlet, a first drive channel arrangedbetween the first drive port and the first and second distributionchambers, and a second drive channel between the second drive port andthe first and second distribution chambers. The fluid distribution valvefurther has a rotatable first distribution member which is arrangedbetween the first distribution chamber and the first and second drivechannels and which has a distribution aperture, as well as a rotatablesecond distribution member which is arranged between the seconddistribution chamber and the first and second drive channels, and whichalso has a distribution aperture. Each distribution aperture of thefirst distribution member and the second distribution member is adaptedto align with both and opposite first and second drive channels,depending on the rotational position of the first and seconddistribution members.

As the skilled reader will appreciate, the fluid distribution valveaccording to the second aspect of the invention may very well be a partof the downhole well pump assembly according to the first aspect of theinvention.

In an embodiment of the second aspect of the invention, the first andsecond distribution members are arranged on opposite sides of apartition wall comprising a first partition wall bore and a secondpartition wall bore which constitute part of the first and second drivechannels. Moreover, the first and second distribution members areconnected to a common shaft which extends through the partition wall.The shaft and the distribution members can rotate together/co-rotate.

The fluid distribution valve may comprises a main body within which thefollowing are arranged:

-   -   the first and second distribution chamber;    -   the partition wall;    -   the first and second drive channels;    -   an output channel and a first distribution chamber mouth which        connect the first distribution chamber to the drive fluid        output;    -   an input channel and a second distribution chamber mouth which        connect the second distribution chamber to the drive fluid        input.

Moreover, the fluid distribution valve may comprise a bypass channelwhich connects the first drive port with the second drive port.

The bypass channel is advantageously a channel which only offers a lowflow rate. I.e. it should be a narrow channel, or a channel having anarrow flow restriction. By means of the bypass channel, some drivefluid may flow into and out of the fluid distribution valve even ifthere is no flow through the first and second drive ports. When, howevera large flow exists through the drive ports, there will be some flowalso through the bypass channel, which then may be construed as a leak.However, by arranging a flow through the first and second drive portswhich is significantly larger than the possible flow through the bypasschannel, this leak through the bypass channel can be made substantiallyinsignificant.

As will be apparent from the detailed description of embodiment below,the distribution member, employed either in the first or second aspectof the invention, may advantageously be disc shaped.

According to a third aspect of the invention, there is provided acollapsible metal bellows which has a cylindrical shape, which isaxially collapsible, and which at one axial end has a drive fluid inletand outlet end and which at the opposite axial end has a bellows closureflange. It further comprises a collapse restriction means which at thedrive fluid inlet and outlet end comprises a drive fluid valve membermovable between an open valve position and a closed valve position, andwhich is biased towards the open valve position. At the opposite axialend it comprises an actuation member which protrudes with an axialdistance into the metal bellows, and which upon axial movement of thebellows closure flange towards the drive fluid inlet and outlet end isconfigured to abut against and move the drive fluid valve member towardsthe closed valve position.

In such an embodiment, the drive fluid valve member may have a valvemember opening that constitutes fluid communication between the interiorand exterior of the metal bellows, wherein the valve member opening ispartially closed when the fluid valve member is in an intermediate valveposition.

EXAMPLES OF EMBODIMENT

While the various aspects of the invention have been discussed ingeneral terms above, a non-limiting example of embodiment will bediscussed in the following with reference to the appending drawings, inwhich

FIG. 1 is a perspective view of a downhole pump assembly according tothe invention;

FIG. 2 is a schematic diagram illustrating elements of the pumpassembly;

FIG. 3 is a schematic illustration of a fluid distribution valve, herein form of a hydraulic slide valve;

FIG. 4 is a cross section view through a pumping section comprising twopump units;

FIG. 5 is a schematic diagram of the function of the pumping section;

FIG. 6 and FIG. 7 are cross section views of a pump unit, having anexpanded and a collapsed metal bellows, respectively;

FIG. 8 is a cross section view of a drive fluid assembly;

FIG. 9 is a cross section, perspective view of a main end body which isconfigured for connection to an axial end of the metal bellows;

FIG. 10 is a cross section side view through the components shown inFIG. 9;

FIG. 11 is a cross section view through a drive fluid valve member;

FIG. 12 another cross section, perspective view according to FIG. 9,however with the drive fluid valve member in a closed state;

FIG. 13 is a perspective view of a fluid distribution valve according tothe second aspect of the invention;

FIG. 14 is a perspective, cross section view through the fluiddistribution valve shown in FIG. 13;

FIG. 15 is a side cross section view of the fluid distribution valve;

FIG. 16 is a side cross section view of the fluid distribution valvealong a different plane;

FIG. 17 is a side view of the fluid distribution valve, with indicationof the cross section view planes;

FIG. 18 is a separate perspective view of a distribution member in theform of a distribution disc;

FIG. 19 is a perspective view of two distribution discs mounted on acommon shaft;

FIG. 20 is a side view of the two distribution discs and the shaft shownin FIG. 19;

FIG. 21 is a cross section top view through the fluid distributionvalve;

FIG. 22 is another cross section side view of the fluid distributionvalve;

FIG. 23 is another cross section top view of the fluid distributionvalve; and

FIG. 24 is a schematic view of an alternative embodiment according tothe invention.

FIG. 1 is a perspective view showing an example of a downhole well pumpassembly 1 according to the invention. The assembly has a pumpingsection 3, which contains two pump units, and a drive fluid assembly 5,which is configured to provide pressurized hydraulic drive fluid to thepumping section 3.

As can be appreciated from FIG. 1, the downhole well pump assembly 1 hasa tubular, elongated configuration. It is well suited for beingintegrated or installed in a casing, production tubing, or an open hole(not shown) (i.e. a well). This being said, one can also imagine thepump assembly being suspended on a wire or an umbilical.

FIG. 2 is a schematic representation of the various components of thepump assembly 1. The pumping section 3 has a first pump unit 7 a and asecond pump unit 7 b, which in FIG. 2 are represented by bellows (whichwill be discussed below). First and second pump units 7 a, 7 b areconnected to a hydraulic drive line, namely a first hydraulic drive line9 a or a second hydraulic drive line 9 b, respectively. When in use,drive fluid is flown into and out of the pump units 7 a, 7 b (i.e. thebellows) through the hydraulic drive lines 9 a, 9 b.

The hydraulic drive lines 9 a, 9 b connect to a drive fluid distributionvalve 11. In this embodiment, the drive fluid distribution valve is inthe form of a continuous rotating distribution valve 11 (CRDV). Theoperation of the CRDV 11 will be thoroughly discussed further below.However, its function may be compared with the slide valve 211 depictedin FIG. 3. The CRDV 11 will, in the setup shown in FIG. 2, receive thehydraulic drive fluid through its inlet line 13, and the hydraulic drivefluid will exit through its outlet line 15. As illustrated with thesliding valve 211 in FIG. 3, it has two functional modes. In a firstmode, the received drive fluid will be guided to the first hydraulicdrive line 9 a, while it receives drive fluid from the second hydraulicdrive line 9 b. In the second mode, it will guide the drive fluid to thesecond hydraulic drive line 9 b, while receiving drive fluid from thefirst drive line 9 a. As illustrated with the sliding valve in FIG. 3,the two modes are determined by the position of the sliding valve. Withsuch a sliding valve 211, the position (mode) of the valve body maytypically be controlled with an electric control means 219,schematically illustrated in FIG. 3.

In the schematic illustration of FIG. 2, the inlet line 13 and theoutlet line 15 both extend between the CRDV 11 and a drive fluid pump17. The drive fluid pump 17 delivers pressurized hydraulic drive fluidto the inlet line 13. Delivered drive fluid is guided into one of thepump units 7 a, 7 b. Which of the two pump units 7 a, 7 b which receivesthe drive fluid, is governed by the current mode of the CRDV 11 (i.e.which one of the two possible modes). Drive fluid returning to the drivefluid pump 17, flows through the outlet line 15.

Notably, since the flow direction out from and into the drive fluid pump17 never changes, the drive fluid pump 17 can run continuously withoutchanging its direction. In this embodiment, the drive fluid pump 17 is arotating positive displacement hydraulic pump.

In addition to the inlet line 13 and the outlet line 15, there is also agear 19 arranged between the drive fluid pump 17 and the CRDV 11. Thegear 19 connects to a (not shown) rotating part of the drive fluid pump17. Also, it connects to a rotating part of the CRDV 11. The gear 19governs changing of the modes of the CRDV 11. For instance, the CRDV 11may change mode for every 50^(th) revolution in the drive fluid pump 17.Thus, the gear 19 does not transmit power used for pumping, but rathergoverns the mode of the CRDV 11, and hence the flow direction within thetwo hydraulic drive lines 9 a, 9 b.

Functionally arranged between the two hydraulic drive lines 9 a, 9 b,there is also a bypass channel 21. The bypass channel 21 has only asmall flow aperture and will substantially not affect the pumping duringnormal pumping speed. The function and object of the bypass channel 21will be explained further below, together with discussion of the CRDV11.

The drive fluid pump 17 is powered by a drive motor 23. The drive motor23 can advantageously be a hydraulic motor powered by hydraulic fluidthrough a hydraulic power line 25. When in use downhole, the hydraulicpower line 25 typically extends upwardly through the well bore, towardsthe surface. A hydraulic return line 27 is also arranged. Instead of ahydraulic drive motor 23, another type of motor could also be used forpowering the drive fluid pump 17, such as an electric motor. For someembodiments, one could omit the return line 27, and dump the fluiddelivered through the power line to the environment. For instance, ifusing a steam/gas turbine as a drive motor 23, one may be able to dumpsteam/gas into certain types of wells.

In this embodiment, the rotational connection between the drive motor 23and the drive fluid pump 17 is a magnetic coupling 29. In this manner,one is able to separate the drive fluid pump 17 and the drive motor 23in separate chambers. However, it would also be possible to connect themwith a rotating shaft extending between the drive fluid pump 17 and thedrive motor 23.

The pumping section 3 and the drive fluid assembly 5 shown assembledtogether in FIG. 1, are shown separately with cross section views inFIG. 4 and FIG. 8. The pumping section 3 has a first pump unit 7 a and asecond pump unit 7 b. Each pump unit 7 a, 7 b has a metal bellows 31arranged in a pump chamber 33. The pump chamber 33 is arranged within apump housing 35. Moreover, the pump chamber 33 communicates with theoutside of the pump housing 35 through an inlet check valve 37 and anoutlet check valve 39. Each check valve 37, 39 have a closing member 41which is adapted to move into and out of abutment with a valve seat 43.The closing member 41 is biased against the valve seat 43 with a checkvalve spring 45, and opens only upon a certain pressure drop over thevalve 37, 39 (in one direction only).

Arranged in parallel with both pump units 7 a, 7 b are bypass channels40. One bypass channel which is adjacent the first pump unit 7 a,communicates with the inlet check valve of the second pump unit 7 b. Theother bypass channel 40, being adjacent the second pump unit 7 b,communicates with the outlet check valve 39 of the first pump unit 7 a(i.e. guiding pumped fluid exiting the first pump unit 7 a).

The inlet and outlet check valves 37, 39 are arranged at opposite endsof the pump chamber 33 which in this embodiment has a cylindricalconfiguration. Between the inlet check valve 37 and the outlet checkvalve 39, the bellows 31 is arranged. The bellows 31 is advantageously ametal bellows which may endure a large number of cycles before beingworn out.

The function of the two pump units 7 a, 7 b shown in the pumping section3 in FIG. 4 is illustrated with the schematic diagram in FIG. 5. Herethe check valves 37, 39 are illustrated with a ball being the closingmember 41, which close against the valve seat 43. It will be understoodthat by inflating and collapsing the bellows 31, each pump unit willforce out (pump out) the pumped fluid, and receive more fluid to bepumped, respectively. Indeed, in order to achieve the pumping function,only one pump unit 7 a, 7 b would suffice. In the shown embodiment, thedownhole well pump assembly 1 has two pump units 7 a, 7 b. In otherembodiments, one could imagine three, four, or even more pump units inthe same assembly.

FIG. 6 and FIG. 7 illustrate the pump unit 7 a in more detail. In FIG.6, the bellows 31 is in an expanded mode. In this position, it is readyto be collapsed. When collapsing, drive fluid within the bellows 31 isflown out from the bellows 31. The pumped fluid, such ashydrocarbon-containing fluid from a hydrocarbon reservoir, will thenfill the pump chamber 33. That is, as the bellows 31 collapses, thepressure in the pumped fluid outside the pump housing 35 will open theinlet check valve 37, and thereby enter the pump chamber 33. The pumpedfluid may flow through a not shown inlet opening in an end flange 47, inassociation with the valve seat 43. This continues until the bellows 31has reached its collapsed mode. This collapsed mode is shown in FIG. 7.

Thus, when in the collapsed mode, shown in FIG. 7, the bellows 31 isready to be filled with drive fluid, thereby moving it back towards theexpanded mode. Drive fluid is flown into the bellows 31 with sufficientpressure to force the pumped fluid out through the outlet check valve39.

Notably, there is some space between the outer portion of the bellows 31and the inner face of the pump housing 33, through which the pumpedfluid may flow.

Contrary to the pumped fluid, which enters and leaves the pump chamber33 at different positions (different check valves 37, 39), the drivefluid enters and leaves the bellows 31 through the same drive fluidchannel 49. The drive fluid channel 49 is connected to one of thehydraulic drive lines 9 a, 9 b schematically shown in FIG. 2.

FIG. 8 depicts a cross section view through the drive fluid assembly 5.Connected to the hydraulic power line 25 and the hydraulic return line27 (cf. FIG. 2) is the drive motor 23. The drive motor 23 is driven byhydraulic fluid and rotates the drive fluid pump 17. In this embodiment,a magnetic coupling 29 connects the drive motor 23 to the drive fluidpump 17. Corresponding to the pump units 7 a, 7 b, the drive fluidassembly 5 also has a bypass channel 40, through which pumped fluid mayflow. A rotating output 16 of the drive fluid pump 17 is connected to areduction gear 19, which further connects to the continuous rotatingdistribution valve 11 (CRDV). The functional equipment of the drivefluid assembly 5 is mounted within a drive fluid assembly housing 30.

The drive motor 23, magnetic coupling 29, the reduction gear 19 and thedrive fluid pump 17 can be conventional equipment and will need nofurther description herein, as such equipment is known to the skilledperson.

For many types of bellows, and in particular the metal bellows 31 of thetype discussed in this embodiment, it is imperative that the pressuredrop over the bellows walls is small. They are not designed to endureany significant pressure drops. Thus, the pressure of the drive fluidwithin the bellows 31 should be substantially the same as the pressurein the pumped fluid within the pump chamber 33, outside the bellows.

Also, such bellows, of the type shown in this embodiment, should not betotally collapsed. That is, the collapsing of the bellows should stopbefore reaching the maximum degree of collapsing. Prevention of suchmaximum collapsing increases the lifetime of such bellows.

These two requirements can be met by proper control of the drive fluidflow into and out of the bellows 31.

The disclosed pump units 7 a, 7 b are however, in addition to suchproper control of the drive fluid (which will be discussed below),provided with a collapse restriction means 50.

For the discussion of the collapse restriction means 50, reference isnow made to FIG. 9. In this perspective cross section view, the outletcheck valve 39, as well as adjacent components, are shown. The drivefluid channel 49 (cf. also FIG. 6 and FIG. 7) extends through a portionof a main end body 51. The main end body 51 is arranged in associationwith the outlet check valve 39, and is permanently fixed to one axialend of the bellows 31 (cf. FIG. 6 and FIG. 7). As a part of the drivefluid channel 49, there is a drive fluid valve bore 53. At an end of thedrive fluid valve bore 53, there is a drive fluid valve member 55 whichis biased with a drive fluid valve spring 57 towards an open valveposition. This open valve position is shown in FIG. 9.

The drive fluid valve member 55 is a substantially cup-shaped memberhaving a collar 59 at its open end. The collar 59 is adapted to abutagainst an abutment shoulder 61 of a drive fluid valve disk 63, when inthe open valve position (FIG. 9). When the collar 59 abuts against theabutment shoulder 61, the drive fluid valve member 55 protrudes througha drive fluid valve aperture 65 in the drive fluid valve disk 63. Whenin this position, valve member openings 67 are positioned within thebellows 31, so that drive fluid may flow into or out of the bellows 31through the valve member openings 67. The valve member openings 67 arepositioned in the wall of the drive fluid valve member 55. As a skilledperson will appreciate, only one valve member opening would 67 suffice.

Reference is now made to the cross section view of FIG. 10, showing thesame components as in FIG. 9. In the situation shown in FIG. 10, thedrive fluid valve member 55 has been moved further into the drive fluidvalve bore 53, thereby compressing the drive fluid valve spring 57. Whenin this position, which may be termed an intermediate valve position,only a portion of the valve member openings 67 are exposed against theinner compartment of the bellows 31. As a result, the effective area ofthe valve member openings 67 is reduced, and the flow rate of drivefluid into or out from the bellows 31 is reduced.

In the shown embodiment, the valve member openings 67 have a tapered ortriangular shape, wherein the narrower portion is the last portion beingclosed when the drive fluid valve closes, and the first portion beingopened when the drive fluid valve opens.

FIG. 11 is a cross section showing only a portion of the main end body51. In the situation shown in FIG. 11, the drive fluid valve member 55has been moved all the way to the closed position. In this closedposition, there is no communication between the valve member openings 67and the interior of the bellows 31. Hence, no drive fluid can out fromthe bellows through the drive fluid channel 49. FIG. 12 depicts the sameclosed situation as in FIG. 11 with a perspective cross section viewcorresponding to FIG. 9. Notably, the drive fluid valve spring 57 hasbeen collapsed within the drive fluid valve bore 53. Also, the closedend face 69 of the drive fluid valve member 55 is flush with the drivefluid valve disk 63. The outer circumferential face of the drive fluidvalve member 55 seals against the radially inwardly facing surface ofthe drive fluid valve aperture 65.

The manner in which the drive fluid valve member 55 is, or may be, moveddown into or towards the closed position (FIG. 11 and FIG. 12), will nowbe discussed with reference to FIG. 6 and FIG. 7. The axial end of thebellows 31 which is opposite of the outlet check valve 39, is attachedto a bellows closure flange 71. The bellows closure flange 71 isarranged opposite a drive fluid inlet end and outlet 72 of the bellows31. The bellows closure flange 71 fulfils two main objects. First ofall, it closes the axial end of the bellows 31. Also however, it isadapted to force the drive fluid valve member 55 towards and/or into theclosed position (FIG. 11 and FIG. 12). The bellows closure flange 71 hasan actuation member 73 which protrudes an axial distance into thebellows 31.

In the situation shown in FIG. 7, the bellows 31 has been collapsed to acorrect collapsing position. Thus, the bellows 31 is not fully collapsedand could be further collapsed. However, as discussed above, in order toenhance the lifetime of the bellows 31, it is an object to avoidcollapsing the bellows beyond a certain degree or beyond a certainlevel. For instance, it may be advantageous to only flow out 70% of thevolume which is contained in the bellows 31 when in the expandedposition (FIG. 6).

Still referring to FIG. 7, if the bellows 31 would have been collapsedfurther, the actuation member 73 of the bellows closure flange 71 wouldabut against the drive fluid valve member 55, and move the drive fluidvalve member 55 towards the closed position. As an effect of thismovement, as discussed above, the effective area of the valve memberopenings 67 would decrease, and the collapsing rate would also decrease.If collapsing the bellows 31 even further, the actuation member 73 wouldmove the drive fluid valve member 55 all the way to the closed position,thereby preventing further collapsing of the bellows 31.

In the shown embodiment, the actuation member 73 has the shape of a cup.In the expanded position, as shown in FIG. 6, the cup shape of theactuation member 73 accommodates a portion of the structure thatsupports the check valve spring 45 of the inlet check valve 37. However,as will be understood by the person skilled in the art, the actuationmember 73 may also exhibit other configurations which would be suitedfor abutting against the drive fluid valve member 55.

As a result of the collapse restriction means 50, it is not possible tocollapse the bellows 31 beyond a predetermined degree of collapse. Suchdegree can easily be chosen by appropriate dimensioning of the actuationmember 73 of the bellows closure flange 71, and/or the drive fluid valvemember 55. In practical use, it is however an object to control the flowof drive fluid in such manner that the collapse restriction means 50does not come into use.

As discussed above, the collapse restriction means 50 will restrict thebellows 31 from collapsing excessively. When being used with thedownhole well pump assembly 1, as schematically depicted in FIG. 2, itwill also restrict the bellows 31 from becoming excessively inflated.This is because the assembly 1 contains a given amount of drive fluid.Indeed, drive fluid inflated in one bellows 31 is delivered from acollapsing other bellows 31. Thus, when the bellows 31 which iscollapsing is refrained from collapsing further, it cannot give out moredrive fluid for inflating the other bellows 31.

In the shown embodiment (FIG. 9 to FIG. 12), the valve member opening 67has a triangular shape, with a narrow portion being the last portion toclosed off when the opening closes. Other shapes are however alsopossible, for instance a rectangular shape or a circular shape. Sincethe velocity, with which the drive fluid valve member 55 and thus thevalve member opening 67 is closed, depends on the available flow-throughaperture of the valve member opening 67, this velocity will deceleratewhen the drive fluid valve member 55 is moved towards the closedposition.

In the following, the continuous rotating distribution valve 11 (CRDV)will be discussed. FIG. 13 depicts the CRDV 11 with a perspective view.The CRDV 11 has an input section 101 and an output section 103. At theinput section 101, the reduction gear 19 is arranged. The reduction gear19 has a rotating output, as well as a rotating input which connects toa rotating output 16 of the drive fluid pump 17 (cf. FIG. 8). At theinput section 101 are also arranged a drive fluid inlet 113 and a drivefluid outlet 115. When used with the embodiment discussed above (e.g. asshown in FIG. 1 to FIG. 8) the drive fluid inlet 113 and drive fluidoutlet 115 are connected to the inlet line 13 and outlet line 15,respectively (cf. FIG. 2). At the output section 103, the CRDV 11 hastwo drive ports, namely a first drive port 109 a and a second drive port109 b. When used in the above embodiment of the downhole well pumpassembly 1, the first and second drive ports 109 a, 109 b connect to thefirst and second hydraulic drive lines 9 a, 9 b, respectively (FIG. 2).Thus, the drive ports 109 a, 109 b are then functionally connected tothe interior of the metal bellows 31. Moreover, the inlet line 13 fromthe drive fluid pump 17 will communicate with one of the metal bellows31, while the outlet line 15 of the drive fluid pump 17 will communicatewith the other one of the metal bellows 31.

The reduction gear 19 may be of various types and will be chosen by theskilled person according to needs. As reduction gears are well known tothe skilled person, its function will not be discussed herein. Forsimplicity, the reduction gear 19 is in the drawings merely shown as asingle piece.

FIG. 14 is a perspective cross section view through the CRDV 11, whileFIG. 15 is a cross section side view through the CRDV 11. The CRDV 11has a main body 105. The main body 105 has been manufactured from asolid metal cylinder. From each axial end of the main body 105, a firstdistribution chamber 107 and a second distribution chamber 111 has beenmachined. Between the first and second distribution chambers 107, 111, apartition wall 117 remains. Through the partition wall 117, a first andsecond axially directed partition wall bores 119 a, 119 b are drilled.The first and second partition wall bores 119 a, 119 b constitute partof respective first and second drive channels 121 a, 121 b. The firstand second drive channels 121 a, 121 b lead to respective first andsecond drive ports 109 a, 109 b, and are able to connect the first andsecond distribution chambers 107, 111 to the drive ports 109 a, 109 b.When used with the pumping section 3, as discussed above, the first andsecond drive channels 121 a, 121 b thus lead to the metal bellows 31.

As seen in FIG. 14 and in FIG. 15, arranged at the input section 101, aninput section flange 123 is attached to the main body 105.Correspondingly, an output section flange 125 is attached at the outputsection 103. The output and input section flanges 123, 125 close thefirst and second distribution chambers 107, 111, respectively.

Referring now to FIG. 16, which is a cross section view through the CRDV11 along the plane R-R indicated in FIG. 17. The first and second driveports 109 a, 109 b are arranged in the output section flange 125. Thedrive ports 109 a, 109 b mate with axially extending drive channel bores127 in the main body 105.

Moreover, between the outer face of the main body 105 and the partitionwall bores 119 a, 119 b, there are drilled two cross bores 129. Therespective cross bores 129 connect the respective partition wall bores119 a, 119 b (cf. FIG. 14 and FIG. 15) and the drive channel bores 127.Thus, each of the first and second drive channels 121 a, 121 b, whichextend between the first and second distribution chambers 107, 111 andthe first and second drive ports 109 a, 109 b, comprises a first orsecond partition wall bore 119 a, 119 b, one drive channel bore 127, andone cross bore 129. The cross bores 129, which are drilled in adirection crosswise to the axial direction, are blinded off at theexternal face of the main body with a blinding arrangement 131.

It is still referred to FIG. 16, showing the two drive channel bores 127that connect to the respective drive ports 109 a, 109 b. Through a partof the main body 105, a bypass channel bore 133 connects the two drivechannel bores 127 and this the two drive ports 109 a, 109 b. Within thebypass channel bore 133 is the bypass channel 21 (cf. also the schematicillustration of FIG. 2). Advantageously, the bypass channel 21 can beconstituted by a threaded piece which the operator can install accordingto desired flow through it. At the outer perimeter of the main body 105,the bypass channel bore 133 is blinded off with a bypass channel boreblinding arrangement 135 (also shown in FIG. 13).

Hence, the first and second drive ports 109 a, 109 b each communicateswith a respective first or second partition wall bore 119 a, 119 b (cf.FIG. 15). In the situation shown in FIG. 15, the first drive port 109 acommunicates with the first distribution chamber 107. The second driveport 109 b communicates with the second distribution chamber 111.Between both partition wall bores 119 a, 119 b and the firstdistribution chamber 107, there is arranged a first distribution member,here in the form of a first distribution disc 137. The firstdistribution disc 137 comprises a distribution aperture 139 extendingthrough the first distribution disc 137. In the shown position (FIG.15), the distribution aperture 139 of the first distribution disc 137connects the first distribution chamber 137 to the first partition wallbore 119 a. Moreover, the first distribution disc 137 closescommunication between the first distribution chamber 107 and the secondpartition wall bore 119 b.

Correspondingly, on the opposite side of the partition wall 117, asecond distribution member, here in the form of a second distributiondisc 141, having also a distribution aperture 139, is arranged. Thesecond distribution disc 141 is positioned in such way that it closesoff communication between the second distribution chamber 111 and thefirst partition wall bore 119 a. However, the second distributionchamber 111 communicates with the second partition wall bore 119 bthrough the distribution aperture 139 of the second distribution disc141.

FIG. 18 illustrates the first distribution disc 137 (which can beidentical to the second distribution disc 141), separated from the CRDV11. Centrally arranged in the first distribution disc 137 it has acentral bore 143. The central bore 143 is arranged to receive a discshaft 145 which extend through the partition wall 117. As can be seen inFIG. 14 and FIG. 15, both the first and the second distribution discs137, 141 connects to the disc shaft 145. The disc shaft 145 connects tothe gear 19, and hence rotates the first and second distribution discs137, 141 when the drive fluid pump 17 is operated.

It will be appreciated by the skilled person, that the CRDV 11 also maybe used in other applications than the one shown herein. In suchapplications, the disc shaft 145 may connect to and be rotated by othercomponents.

Advantageously, the first and second distribution discs 137, 141 connectto the disc shaft 145 with a spline connection. Thus, they may movesomewhat in the axial direction, with respect to the disc shaft 145.Belleville springs 147 are arranged between respective distributiondiscs 137, 141 and input and output section flanges 123, 125, asillustrated in FIG. 14 and FIG. 15. A spring disc 149 is interposedbetween the Belleville spring 147 and the distribution disc 137, 141.The spring discs 149 transfers biasing force from the Belleville springs147 onto the distribution discs 137, 141. In this way, the distributiondiscs 137, 141 are biased towards the partition wall 117.

FIG. 19 and FIG. 20 depict the first and second distribution discs 137,141 arranged on the disc shaft 145. When in operation, these threecomponents rotate together.

FIG. 21 is a cross section through the CRDV 11 along a planeperpendicular to its axial direction. In the position shown in FIG. 21,the distribution aperture 139 of the first distribution disc 137 ispartially aligned with the second partition wall bore 119 b.

Referring again to FIG. 15, the first distribution chamber 107communicates with the drive fluid outlet 115 via a first distributionchamber mouth 151. The first distribution chamber mouth 151 and thedrive fluid outlet 115 are connected with an output channel 153extending in an axial direction through a part of the main body 105.Similarly, in the second distribution chamber 111 there is a seconddistribution chamber mouth 155. The second distribution chamber mouth155 communicates with the drive fluid inlet 113 via an input channel157. Corresponding to the output channel 153, the input channel 157extends in an axial direction through a part of the main body 105. Moreprecisely, it extends from the drive fluid inlet 113 to the seconddistribution chamber mouth 155.

The cross section of FIG. 21 depicts the output channel 153 and theinput channel 157 within the main body 105. Also shown in FIG. 21 is theinterface between the output channel 153 and the first distributionchamber mouth 151.

Thus, in the embodiment discussed above, such as with reference to FIG.2, the inlet line 13 communicates with the second distribution chamber111. Moreover, the outlet line 15 communicates with the firstdistribution chamber 107.

Hence, when the first distribution disc 137 and the second distributiondisc 141 are in the position shown in FIG. 15, drive fluid will bepumped (by the drive fluid pump 17) into the second distribution chamber111, and further through the distribution aperture 139 of the seconddistribution disc 141, and into the second drive port 109 b.Correspondingly, drive fluid will flow from the first drive port 109 aand into the first distribution chamber 107, and out through the drivefluid outlet 115.

When the disc shaft 145, along with the first and second distributiondiscs 137, 141 rotates 180 degrees, the flow directions through the twodrive ports 109 will have been changed. The pumped drive fluid will thenbe pumped out of the CRDV 11 through the first drive port 109 a, whiledrive fluid will enter the CRDV 11 through the second drive port 109 b.

The configuration of the distribution aperture 139 in the firstdistribution disc 137 and in the second distribution disc 141, ispreferably such that there always will be a some flow through the CRDV11. That is, the first and second distribution discs 137, 141 are partlyopen simultaneously, when switching between the first and second modes.

FIG. 22 is a cross section view of the CRDV 11, along the plane U-Uindicated in FIG. 17.

FIG. 23 is another cross section view through the CRDV 11, along theplane T-T in FIG. 17. In this view, the cross bores 129 are illustrated,extending in a direction crosswise to the axial direction.

As appears particularly from FIG. 21 and FIG. 23, the main body of theCRDV 11 has a cylindrical shape with a circular cross section. Moreover,the disc shaft 145 is arranged somewhat displaced with respect to thecenter axis of the main body 105. The first and second distributionchambers 101, 111 are also eccentrically arranged within the main body105. This makes space available within the main body 105 to accommodatethe input channel 157, output channel 153, and the drive channel bores127 (cf. FIG. 16).

Referring again to the schematic illustration of FIG. 2. The drive fluidpump 17 can be continuously run, pumping drive fluid from the outletline 15 to the inlet line 13. As discussed, the direction of flow intoand out from the drive fluid pump 17 is not changed. By means of theCRDV 11, which was discussed above, drive fluid is pumped from a firstpump unit 7 a and into a second pump unit 7 b a first mode, while fromthe second pump unit 7 b and into the first pump unit 7 a when in asecond mode. Thus, there is no need for an additional reservoir of pumpfluid, as the bellows 31 (pump units) function as pump fluid reservoirsfor each other.

By knowing the pumped volume out from the drive fluid pump 17 perrevolution of the drive fluid pump 17, one can make sure that a correctvolume of drive fluid is pumped into and flown out from each pump unit 7a, 7 b by appropriate use or design of the gear 19 and the CRDV 11.

As an example, a drive fluid volume of 5 liters shall be pumped into thefirst pump unit 7 a. Then, 5 liters shall be flown out from the secondpump unit 7 b. If the drive fluid pump 17 feeds out 0.1 liters perrevolution, the drive fluid pump 17 shall rotate 50 revolutions forfilling the first pump unit 7 a, and empty the second pump unit 7 b. Thegear 19 should then be a reduction gear, so designed that the disc shaft145 (cf. FIG. 14 and FIG. 15) of the CRDV 11 will rotate 180 degrees asthe drive fluid pump 17 rotates 50 rounds. Then, by further, continuousrotation of the disc shaft 145, the CRDV 11 changes mode (alters thedirection of the drive fluid through the hydraulic drive lines 9 a, 9b).

Notably, the repeated pumping into and out of the two bellows 31 or pumpunits 7 a, 7 b, is achieved without usage of electrical controls. Theoperator may simply pump hydraulic power fluid through the hydraulicpower line 25 (FIG. 2).

Before starting normal operation of the downhole well pump assembly 1,the operator may not know if the position of the CRDV 11 is correct withrespect to the filling level of the two bellows 31 (pump units 7 a, 7b). If the drive unit pump 17 is started with normal speed while the twobellows 31 are not in the correct filling modes, the bellows 31 could beharmed. (A precaution means against excessive collapsing is howeverrepresented by the collapse restriction means 50 discussed above.) Inorder to avoid a situation where drive fluid is pumped into an alreadyfully expanded bellows 31, the operator may run the drive fluid pump 17very slowly during a startup phase. Such slow running of the drive fluidpump 17 will ensure that drive fluid, instead of entering an alreadyexpanded bellows 31 (pump unit 7 a, 7 b), will flow through the bypasschannel 21 (cf. FIG. 2 and FIG. 16). Such a startup phase will protectthe bellows 31 from excessive inflation and excessive deflation. Byrunning the drive motor 23, the drive fluid pump 17, and thereby theCRDV 11 in this slow pace, in the startup phase, the position or mode ofthe CRDV 11 will be aligned with the mode (inflated or deflated/expandedor collapsed) of the bellows 31. Thereafter, the drive fluid pump 17 canbe run with normal, i.e. quicker, speed in order to commence pumping ofthe fluid which shall be pumped by the downhole well pump assembly 1.When running the drive fluid pump 17 with the normal pumping speed, somedrive fluid will escape through the bypass channel 21. However, thisamount can be made sufficiently small to ensure a sufficient efficiencyof the downhole well pump assembly 1. Moreover, if—for some reason—theCRDV 11 should not balance the fluid amounts to the two bellows 31, thiswill be adjusted by some flow through the bypass channel 21. Forinstance, if the CRDV 11 repeatedly delivers more drive fluid to thefirst pump unit 7 a, and less to the second pump unit 7 b, this will becompensated for by some flow through the bypass channel 21.

FIG. 24 depicts a schematic view of an alternative embodiment accordingto the invention. In this embodiment, the downhole well pump assembly 1has four pump units 7 a, 7 b, 7 b wherein two and two bellows (i.e. twopairs of bellows) are placed in a common pump cavity. The four pumpunits 7 may typically be arranged in a row, such as the two pump unitsshown in FIG. 1 and in FIG. 4. By including more pump units 7, thepumping volume per cycle can be increased.

Some embodiments may include more than one pump assemblies according tothe invention. I.e. one can for instance have two or more downhole wellpump assemblies 1 (cf. FIG. 1) arranged in series inside one well.

1. A downhole well pump assembly comprising: a first pump unit and asecond pump unit, each pump unit having a compressible metal bellowsarranged in a housing, the housing being connected to an inlet checkvalve and an outlet check valve; a drive fluid assembly with a firsthydraulic drive line in communication with the inner volume of the metalbellows of the first pump unit and a second hydraulic drive line incommunication with the inner volume of the metal bellows of the secondpump unit, the drive fluid assembly further comprising a drive fluidpump providing hydraulic fluid to the first and second hydraulic drivelines, wherein the drive fluid pump is mechanically connected to a drivemotor which is powered by a power line and which drives the drive fluidpump; and, wherein a drive fluid distribution valve is arranged betweenthe drive fluid pump and the first and second hydraulic drive lines, thedrive fluid distribution valve comprising a drive fluid inlet, a drivefluid outlet, a first drive port and a second drive port, and whereinthe drive fluid distribution valve is interchangeable between; a firstmode, in which the drive fluid inlet is in communication with the firstdrive port, and the drive fluid outlet is in communication with thesecond drive port; and a second mode, in which the drive fluid inlet isin communication with the second drive port, and the drive fluid outletis in communication with the first drive port.
 2. The downhole well pumpassembly according to claim 1, wherein the drive fluid pump comprises arotating output which is functionally connected to the drive fluiddistribution valve, wherein rotation of the rotating output governs thechanging of the drive fluid distribution valve between the first modeand the second mode.
 3. The downhole well pump assembly according toclaim 1, wherein a bypass channel is arranged between the firsthydraulic drive line and the second hydraulic drive line.
 4. Thedownhole well pump assembly according to claim 1, wherein thecompressible bellows in the first and second pump units comprises acollapse restriction means, wherein the collapse restriction means has adrive fluid valve member which is interchangeable between an open and aclosed position.
 5. The downhole well pump assembly according to claim4, wherein the drive fluid valve member is arranged at a drive fluidinlet and outlet end of the compressible bellows, and that a bellowsclosure flange is arranged at the opposite end of the compressiblebellows, wherein an actuation member, which is connected to the bellowsclosure flange, protrudes axially into compressible bellows and isconfigured to abut and thereby move the drive fluid valve member intothe closed position upon movement of the bellows closure flange towardsthe drive fluid inlet and outlet end.
 6. The downhole well pump assemblyaccording to claim 1, wherein the drive fluid distribution valvecomprises: a housing; a first distribution chamber communicating withthe drive fluid outlet; a second distribution chamber communicating withthe drive fluid inlet; a first drive channel arranged between the firstdrive port and the first and second distribution chambers, and a seconddrive channel arranged between the second drive port and the first andsecond distribution chambers; a rotatable first distribution memberwhich is arranged between the first distribution chamber and the firstand second drive channels and which has a distribution aperture, and arotatable second distribution member which is arranged between thesecond distribution chamber and the first and second drive channels, andwhich has a distribution aperture; and wherein each distributionaperture of the first distribution member and the second distributionmember is adapted to align with both and opposite first and second drivechannels, depending on the rotational position of the first and seconddistribution members.
 7. The downhole well pump assembly according toclaim 2, wherein: the first and second distribution members areconnected to a common shaft; the shaft is connected to a reduction gear;and that the reduction gear is connected to the rotating output.
 8. Afluid distribution valve comprising: a housing; a drive fluid inlet; adrive fluid outlet; a first drive port; a second drive port; a firstdistribution chamber in fluid communication with the drive fluid outlet;a second distribution chamber in fluid communication with the drivefluid inlet; a first drive channel arranged between the first drive portand the first and second distribution chambers, and a second drivechannel between the second drive port and the first and seconddistribution chambers; a rotatable first distribution member which isarranged between the first distribution chamber and the first and seconddrive channels and which has a distribution aperture, and a rotatablesecond distribution member which is arranged between the seconddistribution chamber and the first and second drive channels, and whichhas a distribution aperture; and wherein each distribution aperture ofthe first distribution member and the second distribution member isadapted to align with both and opposite first and second drive channels,depending on the rotational position of the first and seconddistribution members.
 9. The fluid distribution valve according to claim8, comprising: wherein the first and second distribution members arearranged on opposite sides of a partition wall comprising a firstpartition wall bore and a second partition wall bore which constitutepart of the first and second drive channels; and wherein the first andsecond distribution members are connected to a common shaft whichextends through the partition wall.
 10. The fluid distribution valveaccording to claim 9, comprising a main body within which the followingare arranged: the first and second distribution chamber; the partitionwall; the first and second drive channels; an output channel and a firstdistribution chamber mouth which connect the first distribution chamberto the drive fluid output; and an input channel and a seconddistribution chamber mouth which connect the second distribution chamberto the drive fluid input.
 11. The fluid distribution valve according toclaim 8, comprising a bypass channel which connects the first drive portwith the second drive port.
 12. A collapsible metal bellows which has acylindrical shape, is axially collapsible, and at one axial end has adrive fluid inlet and outlet end and which at the opposite axial end hasa bellows closure flange, the collapsible metal bellows comprising: acollapse restriction means comprising: at the drive fluid inlet andoutlet end a drive fluid valve member movable between an open valveposition and a closed valve position, and which is biased towards theopen valve position; and at the opposite axial end an actuation memberwhich protrudes with an axial distance into the metal bellows, and whichupon axial movement of the bellows closure flange towards the drivefluid inlet and outlet end is configured to abut and move the drivefluid valve member towards the closed valve position.
 13. Thecollapsible metal bellows according to claim 12, wherein the drive fluidvalve member exhibits a valve member opening constituting fluidcommunication between the interior and exterior of the metal bellows,wherein the valve member opening is partially closed when the fluidvalve member is in an intermediate valve position.